FIG. 7 shows an example of an elliptic cylindrical winding power generating element 1 used for a nonaqueous electrolyte secondary battery. The power generating element 1 is formed by winding a positive electrode 1a and a negative electrode 1b into an elliptic cylindrical shape with separators 1c interposed therebetween. The positive electrode 1a is formed by loading positive active material (a dot-hatched portion) on a surface of a strip of aluminum foil as a substrate and the negative electrode 1b is formed by loading negative active material (a dot-hatched portion) on a surface of a strip of copper foil as a substrate. The positive electrode 1a includes an uncoated portion not coated with the positive active material at an edge portion on a right side in the drawing of the strip of aluminum foil and the negative electrode 1b includes an uncoated portion not coated with the negative active material at an edge portion on a left side in the drawing of the strip of copper foil. By winding the positive electrode 1a and the negative electrode 1b with the separators 1c interposed therebetween while displacing the positive electrode 1a rightward and the negative electrode 1b leftward, only the aluminum foil of the uncoated portion of the positive electrode 1a is wound in layers and protrudes as a group 1d of metal foil from the separators 1c at the right end portion of the power generating element 1 and only the copper foil of the uncoated portion of the negative electrode 1b is wound in layers and protrudes as a group 1e of metal foil from the separators 1c at the left end portion.
One of methods of connecting the group 1d (and the group 1e, similarly) of metal foil of the power generating element 1 to a terminal is to insert a connecting plate portion provided to the other end portion of a current collecting connector, which is connected at its one end portion to the terminal, into a central core portion of the group 1d of metal foil protruding into an elliptic cylindrical shape and to weld the metal foil of the group 1d of metal foil on opposite sides to the connecting plate portion (see Patent Document 1, for example).
Another method of connecting the group 1d (and the group 1e, similarly) of metal foil of the power generating element 1 to the terminal is to divide layers of metal foil of the group 1d to pinch the divided layers of metal foil in V-shaped connecting portions provided to the other end portion of the current collecting connector, which is connected at its one end portion to the terminal, and to weld the metal foil to the connecting portions (see Patent Document 2, for example).
Furthermore, another method of connecting the group 1d (and the group 1e, similarly) of metal foil of the power generating element 1 to the terminal is to bring respective protruding ends of metal foil of the group 1d into contact with the connecting plate portion provided to the other end portion of the current collecting connector, which is connected at its one end portion to the terminal, and to weld the protruding ends to the connecting plate portion (see Patent Document 3, for example).